title: Probing atomic structure in magnetic core/shell nanoparticles using synchrotron radiation.
abstract: Core/shell Fe/Cu and Fe/Au nanoparticles were prepared directly by deposition from the gas phase. A detailed study of the atomic structure in both the cores and shells of the nanoparticles was undertaken by means of extended absorption fine structure (EXAFS) measurements. For Fe/Cu nanoparticles, a Cu shell ∼ 20 monolayers thick appears similar in structure to bulk Cu and is sufficient to cause the structure in the Fe core to switch from body centred cubic (bcc; as in bulk Fe) to face centred cubic. This is not the case for thinner Cu shells, 1-2 monolayers in thickness, in which there is a considerable contraction in nearest-neighbour interatomic distance as the shell structure changes to bcc. In Fe/Au nanoparticles, the crystal structure in the Fe core remains bcc for all Au thicknesses although there is some stretching of the lattice. In thin Au shells ∼ 2 monolayers thick, there is strong contraction in interatomic distances. There does not appear to be significant alloying at the Fe/Au interface.
authors.affiliation: Department of Physics and Astronomy, University of Leicester, Leicester LE1 7RH, UK. bak@le.ac.uk
authors.forename: S H
authors.initials: SH
authors.lastname: Baker
authors.forename: M
authors.initials: M
authors.lastname: Roy
authors.forename: S C
authors.initials: SC
authors.lastname: Thornton
authors.forename: M
authors.initials: M
authors.lastname: Qureshi
authors.forename: C
authors.initials: C
authors.lastname: Binns
mesh_terms: D003300:Copper / Q000737:chemistry; D006046:Gold / Q000737:chemistry; D007501:Iron / Q000737:chemistry; D008280:Magnetics; D008422:Materials Testing; D053768:Metal Nanoparticles / Q000737:chemistry; D008968:Molecular Conformation; D053758:Nanoparticles / Q000737:chemistry; D036103:Nanotechnology / Q000379:methods*; D010316:Particle Size; D010825:Physics / Q000379:methods*; D013499:Surface Properties; D017356:Synchrotrons; D014965:X-Rays
chemical_list: D006046:Gold; D003300:Copper; D007501:Iron